MAX1478

1%-Accurate, Digitally Trimmed, Rail-to-Rail Sensor Signal Conditioner

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Overview

Medium Accuracy (±1%), Single-Chip Sensor Signal Conditioning
Rail-to-Rail^®Output
Sensor Errors Trimmed Using Correction Coefficients Stored in Internal EEPROM-Eliminates Laser Trimming and Potentiometers
Compensates Offset, Offset TC, FSO, FSO TC, and FSO Linearity
Programmable Current Source (0.1mA to 2.0mA) for Sensor Excitation
Fast Signal-Path Settling Time (<1ms)
+5V Single Supply
Accepts Sensor Outputs from +10mV/V to +40mV/V
Fully Analog Signal Path

The MAX1478 highly integrated, analog sensor signal processor is optimized for piezoresistive sensor calibration and compensation without any external components. It includes a programmable current source for sensor excitation, a 3-bit programmable-gain amplifier (PGA), a 128-bit internal EEPROM, and four 12-bit digital-to-analog converters (DACs). Achieving a total error factor within 1% of the sensor's repeatability errors, the MAX1478 compensates offset, offset temperature coefficient, full-span output (FSO), FSO temperature coefficient (FSO TC), and FSO nonlinearity of silicon piezoresistive sensors.

The MAX1478 calibrates and compensates first-order temperature errors by adjusting the offset and span of the input signal via DACs, thereby eliminating the quantization noise associated with digital signal path solutions. Built-in testability features on the MAX1478 result in the integration of three traditional sensor-manufacturing operations into one automated process:

Pretest: Data acquisition of sensor performance under the control of a host test computer.

Calibration and compensation: Computation and storage (in an internal EEPROM) of calibration and compensation coefficients computed by the test computer and downloaded to the MAX1478.

Final test operation: Verification of transducer calibration and compensation without removal from the pretest socket.

Although optimized for use with piezoresistive sensors, the MAX1478 may also be used with other resistive sensors (i.e., accelerometers and strain gauges) with some additional external components.

Applications